Sections 117.105, 117.113, 117.213, 117.451, 117.510, 117.520,
117.530, 117.540, and 117.601 are adopted with changes to the
proposed text as published in the January 9, 1998, issue of the
Texas Register (23 TexReg 319). Sections 117.205 and 117.211
are adopted without changes and will not be republished.

3. Effect of Change. The Federal Clean Air Act (FCAA),
§ 182(f), specifies that required measures for major sources
of volatile organic compounds (VOCs) must also be applied to major
sources of nitrogen oxides (NOx) in ozone nonattainment areas,
unless a demonstration is made that NOx reductions would not
contribute to attainment of the ozone standard. One of the measures
for existing major sources of VOCs is implementation of reasonably
available control technology (RACT) in moderate, serious, and
severe ozone nonattainment areas, required by § 182(b)(2),
(c), and (d). On April 9, 1993, the Texas Air Control Board adopted
revisions to Chapter 117 implementing the federal § 182(f) NOx
requirements in the Houston/Galveston (HGA) and Beaumont/Port
Arthur (BPA) ozone nonattainment areas.

On April 12, 1995, the United States Environmental Protection
Agency (EPA) approved under § 182(f) a temporary exemption
from the federally required NOx RACT measures in HGA and BPA. The
EPA's approval was based on the state's preliminary demonstration,
using Urban Airshed Model (UAM) modeling, that NOx reductions in
HGA and BPA would not lower ozone levels. The temporary exemption
allowed more time to conduct UAM modeling, using data from the
Coastal Oxidant Assessment for Southeast Texas (COAST), an
intensive 1993 field study. These UAM results were judged critical
in determining whether, and to what extent, NOx reductions are
needed to attain the ozone standard. The EPA specified that the
temporary § 182(f) exemption would expire on December 31,
1996. On May 23, 1997, the EPA extended the exemption to December
31, 1997. This additional year allowed the commission to
accommodate improvements in the UAM, using COAST data, and to
better substantiate whether NOx emission reductions would be
required.

In the Fall of 1997, the commission staff completed the COAST
modeling analysis of the airshed of the upper Texas Gulf Coast. The
study indicated that NOx reductions are a necessary step toward the
area's attaining the federal air quality standard for ozone.
Because of the modeling and the rate-of-progress (ROP) requirement
under the FCAA, § 182(c)(2), which requires continuing steady
reductions of the pollutants that contribute to ozone smog, on
November 24, 1997, the commission determined not to seek further
federal waivers from the NOx reduction requirements of the FCAA for
HGA and BPA.

Chapter 117 remained effective during this period of federal
exemption. The final compliance date was extended twice, first to
May 31, 1997, then to May 31, 1999. Therefore, after the expiration
of the temporary federal exemption on December 31, 1997, no
additional rulemaking was required to make the NOx RACT
requirements of Chapter 117 fully effective.

This rulemaking smooths the transition to an ozone control
strategy for HGA and BPA which includes NOx reduction. The
amendments extend the final compliance date of the Chapter 117 NOx
RACT requirements from May 31, 1999 to November 15, 1999. The
extension provides approximately a two-year period to implement NOx
reductions, from the November 24, 1997, date that the commission
decided to implement a NOx-based strategy. A two-year period is
necessary for industry to purchase, install, and test the emission
control equipment and monitoring systems required by Chapter
117.

The other changes to smooth the implementation of the Chapter
117 RACT requirements eliminate the requirement to monitor carbon
monoxide (CO) continuously for certain units. While CO emissions in
some cases may increase as a result of NOx abatement, checking CO
emissions periodically will also be an effective, but less
expensive, means of avoiding problems with excessive CO.

The adopted revision to § 117.105(j) adjusts the compliance
averaging period for CO for any electric utility unit which does
not use continuous emissions monitors (CEMS) or predictive
emissions monitors (PEMS) for CO. The amendments to this subsection
also revise the compliance period to an hourly period, necessary
for these units since compliance must be determined by manual stack
sampling methods. Twenty-four hours of continuous manual sampling
is impractical.

The adopted new § 117.113(k) adds an option to conduct
periodic sampling of CO instead of using CEMS or PEMS for CO for
electric utility units. In addition to the initial compliance
demonstration for CO, indicator of compliance sampling for CO with
a hand-held analyzer is required following certain manual
combustion tuning or burner adjustments. This procedure will
identify any excessive emission that could occur as a result of an
effort to minimize NOx emissions. In addition, the acid rain
monitoring rules require an annual stack test (relative accuracy
test audit) for NOx emissions. The concurrent test of CO emissions
during this audit will not add to expense and will confirm
compliance with the CO limit on a periodic basis.

The adopted revisions to § 117.205(e) and §
117.211(f)(3) add the option of a 24-hour compliance averaging
period for CO for any industrial unit which uses a CEMS or PEMS for
CO. A 24-hour compliance period, which is practical for units which
use CEMS or PEMS, is somewhat easier to comply with than an hourly
period. The adopted revision creates an incentive to use CEMS or
PEMS for CO.

The adoption of new § 117.213(l) adds an option to conduct
periodic sampling of CO from industrial units instead of using CEMS
or PEMS for CO. In addition to the initial compliance demonstration
for CO, indicator of compliance sampling for CO with a hand-held
analyzer is required following certain manual combustion tuning or
burner adjustments. This procedure will identify any excessive
emission that could occur as a result of an effort to minimize NOx
emissions. A concurrent test of CO emissions during the annual
relative accuracy test audit will confirm compliance on a periodic
basis.

The adopted amendments to § § 117.451, 117.510,
117.520, 117.530, 117.540, and 117.601 extend the final compliance
date to November 15, 1999. As previously discussed in this
preamble, this extension creates roughly a two-year implementation
period, which industry needs. This period is consistent with the
original two-year implementation time for the rules and will serve
to minimize the use of the case-specific phased RACT provisions of
§ 117.540. The adopted revisions to § 117.510(5) and
§ 117.520(4) will consistently extend to January 15, 2000, the
submittal date for 30-day rolling average compliance data from CEMS
or PEMS. Various other dates in § 117.540 have also been
consistently revised.

The commission notes that the adopted final compliance date of
November 15, 1999, is 15 days earlier than the compliance date
proposed in the January 9, 1998, Texas Register. This change
was made to assure that the emission reductions will be fully
creditable toward 1999 ROP requirements under the FCAA, §
182(c)(2). The FCAA, § 182(c)(2)(B), requires the 1999 ROP
reductions to occur by November 15, 1999.